The prognostic impact of the smoking status of cancer patients receiving systemic treatment, radiation therapy, and surgery: A systematic review and meta-analysis

•A metanalysis investigated data from 31.785 patients with six different cancer types.•Active smoking during cancer treatment was associated with an impaired OS.•Active smokers suffered from a poorer cancer-specific mortality.•Smoking cessation led to the similar OS and CSM compared to former or never smokers.•Result considered patients receiving surgery, radiation, and systemic treatment.